The present invention relates to a load carrying vehicle.
A particular application of the vehicle relates to one which can be used for the transportation of heavy loads and which facilitates the loading of those heavy loads onto the vehicle.
Throughout the specification the term xe2x80x9ctracking widthxe2x80x9d shall be taken to mean the usual width of the vehicle in its movement over the ground.
In the transportation of large heavy loads such as earthmoving equipment it is conventional practice to use low loader trailer vehicles which are supported on a multiplicity of tyres. The tyres are of necessity of small diameter in order for them to be able to fit beneath the platform. In this regard it is quite common to use 32 wheels arranged in 4 rows of eight. In such an arrangement a complex control system for load-equalisation interconnects the wheels to ensure that the load is spread as evenly as possible over all of the wheels over a range of uneven road conditions for each wheel set. Such a practice has presented a number of disadvantages which include the feature that the control system cannot function effectively over a sufficient range of wheel travel to be able to accommodate severe road irregularities which results in tyre and suspension damage. In addition the spread of support over such a large area results in severe tyre scrub during cornering which also results in damage to the tyres and the suspension components. In addition the use of a large number of wheels which are each provided with their own suspension system and in many cases their own braking system presents a significant maintenance problem. In addition the use of a large number of small brakes leads to problem of uniform application. Furthermore the braking systems that are used are generally unsuited to continuous application on downgrades since they overheat quickly and it is a common characteristic of such vehicles that they are applied continuously for lengthy periods of time,
As an alternative to the above arrangement there have been proposals put forward to support a low loader trailer at its forward end from the prime mover vehicle and from two sets of wheels at its rear end where the rear sets of wheels are supported to be able to pivot away from the rear of the vehicle to permit access to the trailer by a load. In such a case the wheels can be large and of a high carrying capacity since they do not have to be able be received under the vehicle. Examples of such an arrangement are disclosed in U.S. Pat. No. 5,366,336, No. 3,346,131, No. 300,523 and No. 3,119,502. However the arrangements which have been proposed in the past utilise a wheel supported to each side of a central support arm (U.S. Pat. Nos. 5,366,336 and 3,346,131) which requires the use of a multiplicity of axles or support the wheels in a cantilever fashion to one side of a support arm which requires the arm to have sufficient strength to be able to accommodate the stresses created by such cantilevered support as well as the loadings implicit as a result of the load being carried.
The preceding discussion of the background to the invention is intended only to facilitate an understanding of the present invention. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.
Accordingly the invention resides in a load carrying vehicle body comprising a chassis having a forward support and a rearward support, the chassis being adapted to accommodate a load, said rearward support comprising a pair of support members each comprising at least one wheel mounted to one side of a support member, said support members being movable on the chassis between a first position at which the wheels are located within the tracking width of the vehicle and at which the wheels are aligned with the direction of travel of the vehicle and a second position at which the wheels are displaced laterally from the tracking width to provide access to the rear of the chassis, a first looking means provided between the support members, the first locking means adapted to be interengaged when the support members are in the first position to maintain the wheels in the first position and to enable the support members to cooperate with each other in accommodating the stresses and load exerted thereon when in the first position.
According to a preferred feature of the invention a second locking means is provided between each support member and the chassis, the second locking means being engaged when the support members are in the first position to retain the support members in the first position. According to an embodiment of the invention the second locking means also accommodates some of the stresses exerted on the support members when in the first position.
According to a preferred feature of the invention the mounting between the chassis and the support members is articulated to enable the rear of the chassis to be moved from a first position at which the rear end of the chassis is raised from the ground and a second position at which the rear end of the chassis is adjacent to the ground.
According to a preferred feature of the invention, the support members are pivotally mounted to the chassis about an upright axis to enable the wheels to be moved between the first and second position. According to one embodiment the support members each comprise an arm which extends substantially radially from the pivot axis and which support the wheels at a position spaced from the pivot axis.
According to a further preferred feature, two or more wheels are mounted to said one side of each support member. According to one embodiment the at least one wheel is located to the side of each member which is remote from the other support member.
According to a further preferred feature of the invention, said load carrying vehicle body comprises a trailer wherein the forward support comprises a mounting adapted to be supported from a towing vehicle.
The invention will be more fully understood in the light of the following description of several specific embodiments.